Prepare the dough: To a large mixing bowl, add the softened butter, powdered sugar, almond milk, and vanilla extract. Whisk until fully combined and smooth.
Next, add the all-purpose flour, almond flour, and salt. Stir using a spatula or wooden spoon until it forms a smooth dough. At this point, you can divide the dough in half and add the flavorings of your choice (see notes).
Shape each half of the dough into a 20-24 cm (8 inches) long log. It should have a width of about 4 cm (1.5 inches). Tightly wrap each log in a piece of parchment paper (or plastic wrap) and chill in the refrigerator for at least 2 hours.
Bake: Preheat oven to 350 °F (175°C) and line a baking sheet with parchment paper.
If you want to make the sugar coating: pour 1/2 cup of granulated sugar on a plate. Unwrap a roll of dough and roll it into the sugar.
Slice the roll of dough into 1-cm (about 1/2-inch) thick slices. Arrange the cookies on the prepared baking sheet, leaving about 1 inch between each.
Bake for 18-20 minutes or until the edges are slightly golden brown. Let cool for at least 10 minutes before transferring to a cooling rack. Bake the other roll.
Let them cool completely and enjoy! Cookies will keep for up to 5 days in an airtight container.
Notes
Flavors: The amounts below are given to flavor 1/2 batch of the dough:
Vanilla: Add 1/2 teaspoon of vanilla extract.
Matcha: Combine 1 teaspoon of matcha powder with 1 teaspoon of hot water. Add the matcha paste to the dough.
Espresso: Add 1 teaspoon of coffee extract. If you don't have coffee extract, dilute 1 teaspoon of instant coffee in 1 teaspoon of hot water.
Strawberry: Add 1 and ½ tablespoons of freeze-dried strawberry powder and a pinch of beetroot powder (for more color). If you want extra strawberry flavor, add ½ teaspoon of strawberry extract as well.
Double chocolate: Add 1 tablespoon of cacao powder and 3 tablespoons of finely chopped dark chocolate.